Fabric support for metal reinforced inner ply of runflat tire

ABSTRACT

Fabric treatment layers ( 130   a,    130   b,    132   a,    132   b ) are deployed in the sidewall regions of a runflat tire ( 100 ) having a metal-reinforced first ply ( 120 ). In one embodiment, parallel cord, reinforced fabric treatment layers ( 130   a,    130   b,    132   a    132   b ) sandwich the metal forced first ply ( 120 ) and inhibit buckling of the reinforcing cords ( 70 ) of the first ply during runflat operation when the ply cords or wires are bearing compression loads. In another embodiment, a single woven fabric treatment layer ( 170   a,    170   b ) is disposed in each sidewall region ( 152,154 ) at a location immediately axially inward of the metal-reinforced first ply ( 160 ).

TECHNICAL FIELD

The present invention relates to pneumatic, radial ply runflat tiresand, more specifically, to the wedge-insert reinforced sidewalls ofradial ply runflat tires having a metal-reinforced inner ply.

BACKGROUND OF THE INVENTION

Various methods have been devised for enabling the safe continuedoperation of unpressurized or underpressurized passenger-car tireswithout damaging the tire further and without causing poor steering andvehicle handling, over a distance from the place where the tire lost itspressure to a place desired by the driver, such as a service stationwhere the tire can be changed. Loss of tire pressure can result from avariety of causes, including puncture by a foreign object such as a nailor other sharp object piercing the pneumatic tire installed on avehicle.

Pneumatic tires designed for continued operation under conditions ofunpressurization or underpressuration are referred to as extendedmobility technology (EMT) tires or simply runflat tires. Runflat tiresare capable of being driven in the uninflated condition, whereas theconventional pneumatic tire collapses upon itself when uninflated andsupporting a vehicle load. The sidewalls and internal surfaces of EMTtires do not collapse or buckle onto themselves. In general, the terms“EMT” and “runflat” mean that the tire structure alone has sufficientstrength to support the vehicle load when the tire is operated in theuninflated state. In particular, the sidewalls are reinforced to carrythe tire's load without recourse to the use of other supportingstructures or devices that are disposed internal to but separate fromthe tire.

One approach to runflat tire structural design is described in U.S. Pat.No. 4,111,249, entitled the “Banded Tire,” in which a wide hoop orannular band approximately as wide as the tread was placed under thetread. The wide hoop in combination with the rest of the tire structurecould support the vehicle weight in the uninflated condition.

Numerous other constructions and methods have been used to achieveworkable runflat tire designs. Generally, such tires incorporate thereinforced sidewall designs mentioned above. Such sidewalls are thickerand stiffer, so that the tire's load can be carried by the uninflatedtire without otherwise compromising vehicle handling until suchreasonable time as the tire can be repaired or replaced. The specificmethods used in sidewall stiffening include the incorporation of insertsor fillers generally having, in cross-sectional view, a crescent shape.Such inserts, or wedge inserts as they are often called, are locatedwithin the sidewall portion of the tire carcass, which is the region inthe tire usually having the lowest rigidity. In such runflat designs,the entire sidewall has an approximately uniform thickness in the regionextending radially outward from the bead region to the tire shoulder.

The thick sidewalls of such tires, when operated in the uninflatedcondition, experience a net compressive load, though the outer portionsof the sidewalls are necessarily in tension due to the bending stresseswhile the inside portions are correspondingly in compression. This isespecially the case in the regions of the sidewall that are near themidway point between the tire's bead region and that portion of thetread most immediately adjacent to the ground-contacting portion of thetread. Due to the large amounts of rubber required to stiffen thesidewall members, heat buildup (deriving from cyclical flexure of thesidewalls) is a major factor in tire failure especially when the tire isoperated in the uninflated condition for prolonged periods and at highspeeds.

U.S. Pat. No. 5,368,082 ('082), having a common assignee with thepresent application, disclosed the first commercially accepted runflatpneumatic radial ply tire. The '082 patent describes the employment ofspecial sidewall inserts to improve stiffness. Approximately sixadditional pounds of weight per tire was required to support an 800 lbload in this uninflated tire. This earlier invention, although superiorto prior attempts at runflat tire design, still imposed a weight penaltythat could be offset by the elimination of a spare tire and the tirejack. However, this weight penalty was even more problematic forhigh-aspect-ratio tires such as those used with large touring sedans.The required supported weight for an uninflated luxury car tireapproximates 1400 lbs. These taller sidewalled tires, having-aspectratios in the 55% to 65% range or greater, means that the sidewallbending stresses are several times those of the earlier low-aspect-ratiorunflat tires. Such loads meant that the sidewalls and overall tire hadto be stiffened to the point of adversely influencing riding comfort, ofluxury vehicles.

Accordingly, the engineering requirements for runflat tire designrequire that there be none or minimal loss in riding comfort or vehiclehandling.

In very stiff suspension performance type vehicles such as sport carsand various sport/utility vehicles, the ability to providereinforced-sidewall runflat tires was relatively straightforwardcompared to providing similar runflat tires for luxury sedans requiringa softer ride. Light truck and sport utility vehicles, although not assensitive to ride performance, provide a runflat tire market that rangesfrom accepting a stiffer ride to demanding the softer luxury type ride.

Runflat tire design, as disclosed, for example, in U.S. patentapplication Ser. No. 08/865,489, entitled “Runflat Tire with ImprovedCarcass,” is based on the installation of one or more wedge insertswithin each sidewall flex area. The inserts supply the necessarysidewall rigidity in the absence of air pressure during runflatoperation. While the high resistance to compression of the compound ofthe wedge inserts provides the necessary resistance to the collapse ofthe loaded tire without air pressure, this design has several drawbacks.The two most important ones are increased tire weight and heat buildupin the wedge inserts, especially at high speed and during runflatoperation.

During runflat operation, especially at high speed, the heat buildup inthe wedge inserts leads to deterioration and disintegrative failure ofthe tire. Among the methods used to manage heat buildup due to cyclicalflexure of the wedge inserts are the use of low-hysteresis rubbercompounds in the fabrication of the wedge inserts as well as ways toconduct the heat away from the wedge inserts, as described inEP-A-729,853 incorporated in its entirety by reference herein. Anothermethod by which to minimize heat buildup is to decrease the magnitude ofthe flexural strain by adding additional rubber to thesidewall-reinforcing wedge inserts or by incorporating additionalstrengthening structures such as the a metal reinforced first ply, whichis able to carry, with minimal deformation, a large portion of thecompressive part of each sidewall's deflected load. An example of ametal-reinforced first ply is disclosed in Patent Application Serial No.PCT/US98/13929, having a common assignee with the present invention. Themetal-reinforced first ply carries a large portion of the compressiveload on the axially inwardmost side of each wedge insert while alsoserving to redistribute heat and conduct it away from the insert.Accordingly, a runflat tire incorporating such a metal-reinforced firstply contributes to a longer runflat service life and to improved runflathandling, especially at high speeds.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a light-weight,two-ply runflat radial passenger tire, being as defined in one or moreof the appended claims and, as such, having the capability of beingconstructed to accomplish one or more of the following subsidiaryobjects.

An object of the present invention is to provide a two-ply runflatradial passenger tire, having good tire life and vehicle handlingcharacteristics and a satisfactory ride under normal inflationconditions, by incorporating a compression-load-bearing metallicreinforced inner radial ply that is itself reinforced againstcompressive buckling by the use of at least one layer of fabric adjacentto the inner ply in the tire's sidewall regions.

SUMMARY OF THE INVENTION

The present invention relates to a pneumatic radial ply runflat tirehaving a tread, a casing with two sidewalls, two radial carcass pliesextending from and wrapped about two annular beads, an inner liner, awedge insert in each sidewall and a belt reinforcement structure locatedradially between the tread and the plies. The first or inner carcass plyis reinforced with metal which, in the sidewall regions is sandwichedbetween two circumferentially disposed fabric treatments each comprisingparallel-aligned cords oriented at opposite or crossed angles of between20 degrees and 50 degrees with respect to each other. The twocircumferentially disposed fabric treatments have radial width ofbetween 20 percent and 80 percent of the maximum radial reach of therespective wedge inserts, preferably between 40 percent and 60 percentof the radial reach of the respective wedge inserts.

In a second embodiment, a single woven fabric treatment iscircumferentially disposed axially inward of the metal reinforced firstor inner carcass ply within each respective sidewall region of therunflat tire. The single woven fabric treatment in each sidewall regionhas a radial width of between 20 percent and 80 percent of the maximumradial reach of the wedge inserts in the respective sidewall, preferablybetween 40 percent and 60 percent of the radial reach of the respectivewedge inserts.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure operation, and advantages of the presently preferredembodiment of the invention will become further apparent uponconsideration of the following description taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a prior art runflat tire having asingle wedge insert reinforcement in each sidewall;

FIG. 2A is a cross-sectional view of a portion of one sidewall, showingthe wedge insert and the metal-reinforced first or inner ply;

FIG. 2B shows a cross-sectional view of the portion of one sidewallshown in FIG. 2A compressed under a radial load;

FIG. 3 is a cross-sectional view showing two fabric treatments disposedadjacent to the metal-reinforced inner ply;

FIG. 4 is a cross-sectional view showing a single woven fabric treatmentdisposed adjacent to opposite sides of the metal-reinforced inner ply;

FIG. 5 is a cross-sectional view of one embodiment of the runflat tireof the present invention; and

FIG. 6 is a cross-sectional view of a second embodiment of the runflattire of the present invention.

DEFINITIONS

“Apex” means an elastomeric filler located radially above the bead coreand between the plies and the turnup plies.

“Aspect Ratio” means the ratio of the section height of a tire to itssection width; also refers to the cross-sectional profile of the tire; alow-profile tire, for example, has a low aspect ratio.

“Axial” and “Axially” means the lines or directions that are parallel tothe axis of rotation of the tire.

“Bead” or “Bead Core” generally means that part of the tire comprisingan annular tensile member of radially inner beads that are associatedwith holding the tire to the rim; the beads being wrapped by ply cordsand shaped, with or without other reinforcement elements such asflippers, chippers, apexes or fillers, toe guards and chafers.

“Belt Structure” or “Reinforcement Belts” or “Belt Package” means atleast two annular layers or plies of parallel cords, woven or unwoven,underlying the tread, unanchored to the bead, and having both left andright cord angles in the range from 18° to 30° relative to theequatorial plane of the tire.

“Breakers” or “Tire Breakers” means the same as belt or belt structureor reinforcement belts.

“Carcass” means the tire structure apart from the belt structure, tread,undertread over the plies, but including the beads.

“Casing” means the carcass, belt structure, beads, sidewalls and allother components of the tire excepting the tread and undertread.

“Circumferential” most often means circular lines or directionsextending along the perimeter of the surface of the annular treadperpendicular to the axial direction; it can also refer to the directionof the sets of adjacent circular curves whose radii define the axialcurvature of the tread, as viewed in cross section.

“Cord” means one of the reinforcement strands, including fibers, withwhich the plies and belts are reinforced.

“Crown” or “Tire Crown” means the tread, tread shoulders and theimmediately adjacent portions of the sidewalls.

“Equatorial Plane” means the plane perpendicular to the tire's axis ofrotation and passing through the center of its tread; or the planecontaining the circumferential centerline of the tread.

“EMT” means “extended mobility technology” tire, which means the same as“runflat tire”.

“Footprint” means the contact patch or area of contact of the tire treadwith a flat surface at zero speed and under normal load and pressure.

“Gauge” refers to thickness.

“Inner liner” means the layer or layers of elastomer or other materialthat form the inside surface of a tubeless tire and that contain theinflating fluid within the tire.

“Insert” means the same as “wedge insert,” which is the crescent-shapedor wedge-shaped reinforcement typically used to reinforce the sidewallsof runflat-type tires; it also refers to the elastomericnon-crescent-shaped insert that underlies the tread.

“Lateral” means a direction parallel to the axial direction.

“Moment of inertia” or “structural moment of inertia” refers to thestructural rigidity of a beam section or other structure such as,specifically, the sidewall of a tire. A structure, such as a tiresidewall, having a high moment of inertia is more rigid than a similarstructure having a lower moment of inertia.

“Normal inflation pressure” means the specific design inflation pressureat a specified load assigned by the appropriate standards organizationfor the service condition for the tire.

“Normal load” means the specific design inflation pressure and loadassigned by the appropriate standards organization for the servicecondition for the tire.

“Ply” means a cord-reinforced layer of rubber-coated radially deployedor otherwise parallel cords.

“Radial” and “radially” mean directions radially toward or away from theaxis of rotation of the tire.

“Radial ply structure” means the one or more carcass plies or which atleast one ply has reinforcing cords oriented at an angle of between 65°and 90° with respect to the equatorial plane of the tire.

“Radial ply tire” means a belted or circumferentially restrictedpneumatic tire in which at least one ply has cords which extend frombead to bead and are laid at cord angles between 65° and 90° withrespect to the equatorial plane of the tire.

“Runflat” or “runflat tire” is a pneumatic tire that is designed toprovide limited service while uninflated or underinflated.

“Section height” means the radial distance from the nominal rim diameterto the outer diameter of the tire at its equatorial plane.

“Section width” means the maximum linear distance parallel to the axisof the tire and between the exterior of its sidewalls when and after thetire has been inflated at normal pressure for 24 hours, but unloaded,excluding elevations of the sidewalls due to labeling, decoration orprotective bands.

“Shoulder” means the upper portion of sidewall just below the treadedge.

“Sidewall” means that portion of a tire between the tread and the bead.

“Tangential” and “tangentially” refer to segments of circular curvesthat intersect at a point through which can be drawn a single line thatis mutually tangential to both circular segments.

“Tread cap” refers to the tread and the underlying material into whichthe tread pattern is molded.

“Tread width” means the arc length of the tread surface in the planeincludes the axis of rotation of the tire.

“Wedge insert” means the same as “insert,” which is the sidewallreinforcement used in runflat tires.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Prior Art Embodiment

With reference to FIG. 1, a cross section of a prior art pneumaticradial ply runflat tire 10 is illustrated. The tire 10 has a tread 12, abelt structure 14 comprising belts 16,18, a fabric overlay 20 disposedbetween the tread and the belt structure, a pair of sidewall portions22,24, a pair of bead regions 26 a,26 b, and a carcass structure 28. Thecarcass 28 comprises a first of inner ply 30, a second or outer ply 32,and a gas-impervious inner liner 34. The bead regions 26 a,26 b includea pair of inextensible beads 36 a,36 b, and a pair of bead filler apexes38 a,38 b. The sidewalls 22,24 each contain one sidewall wedge insert 40a,40 b, respectively, each of which is disposed between the first ply 30and the second ply 32. Each wedge insert 40 a,40 b imparts to therespective sidewall a greater structural moment of inertia, or rigidity,for resisting the cyclical deformations imposed upon the sidewallsduring runflat operation. Thus the reinforced sidewall portions 22,24 ofcarcass structure 28 give the tire 10 a limited runflat capability.

While other prior art runflat tire designs make use of two wedge insertsin each sidewall, the present invention is described with regard totires having a single wedge insert 40 a,40 b disposed in each sidewall22,24, respectively, between the first ply 30 and the second ply 32.However, it is within the scope of the present invention to incorporatethe additional fabric treatment on either one side or both sides of theinner ply with a runflat tire having two inserts, as shown for examplein FIG. 5A. In such single wedge-insert runflat tire designs, the singlewedge insert in each sidewall is often disposed between the two plies30,32 as shown in FIG. 1, though sometimes each wedge insert is disposedbetween the inner liner 34 and a single radial ply or a double radialply. An example of a single insert is disclosed in Patent ApplicationSerial No. PCT/US98/20567 where is described a tire having one wedgeinsert in each sidewall but without, in one embodiment, an inner liner.

The present invention generally relates to two-ply runflat tires inwhich the first ply is reinforced with more or less radially alignedmetal wires or cords, as disclosed for example in Patent ApplicationSerial No. PCT/US98/13929, having a common assignee with the presentinvention and which is incorporated in its entirety by reference theretoand where there is described a tire similar in appearance to the tire 10shown in FIG. 1 in which the first or inner ply is reinforced with steelwires or cords. During runflat operation, this steel-reinforced firstply is subjected to cyclical compressive forces because it lies on thecompression side of the neutral bending axis within thewedge-insert-reinforced sidewall regions. Additionally, this first ply,because it incorporates metal reinforcing wires or cords, also isintended to conduct flexure-induced heat from the immediate region ofthe wedge inserts, which therefore serves to-improve the runflat servicelife of the tire.

FIG. 2A is a fragmentary cross-sectional view of a sidewall segment 50of a tire having the same general design as the tire shown in FIG. 1,except that the first or inner ply 54 is reinforced with metal wires(monofilaments) or cords 56. A single wedge insert 52, which isequivalent to the wedge inserts 40 a,40 b in FIG. 1, is disposed betweena first or inner ply 54 and a second or outer ply 58 which is reinforcedwith nonmetallic cords (not shown). An inner liner 60, which isfunctionally equivalent to the inner liner 34 of the prior art tire 10shown in FIG. 1, is shown adjacent to and axially inward of the firstply 54.

FIG. 2B shows the sidewall segment 50 of FIG. 2A being bent or deflecteddue to the radially directed compressive forces F which represent theloadings upon the sidewalls of the uninflated tire sidewall duringrunflat operation. The bending effect of the load F upon the sidewallsegment 50 shown in FIG. 2E is such that the metal-reinforced first orinner ply 54 is subjected to compressive stresses while the second outerply 58 is subjected to tensile stresses. The neutral bending axis A—Alies between the two plies, but in a specific location described below.

In FIGS. 2A, 2B, 3 and 4, such parts as the inner liner, the ply layersand the wedge insert are essentially the same despite the use ofdifferent identifying numbers in the respective FIGURES. For example,the wedge insert 52 in FIGS. 2A and 2B is essentially the same as thewedge inserts 64,82,128 a,128 b,168 a and 168 b shown respectively inthe subsequent FIGS. 3 through 6.

In FIG. 2B, the neutral bending axis A—A is shown closer to the firstply 54 than to the second ply 58 because, as those skilled in the artwill recognize the metal reinforcing wires or cords 56 have a muchhigher modulus of elasticity than do the corresponding non-metallic,tensile-stress-bearing reinforcing cords (not shown) of the second ply58. Also, the modulus of elasticity of the elastomeric compound fromwhich the wedge insert 52 is much lower than those of the metalreinforcing cords 56 of the first ply 54 and the non-metal reinforcingcords (not shown) of the second ply 58. In other words, because themodulus of elasticity of the tensile-bearing reinforcing cords of thesecond ply 58 and the compression-bearing reinforcing metal cords 56 ofthe first ply 54 are significantly larger than the modulus of elasticityof the elastomeric compound of which the wedge insert 52 is made, thetwo ply layers are structurally analogous to the flange members of anI-beam while the wedge insert is analogous to the I-beam's web portionwhich separates the two flange portions. However, within the context ofthis I-beam analogy to the rigidifying structure of the sidewall portion50 shown in FIGS. 2A and 2B, the larger modulus of elasticity of thecompression-bearing metal cords or reinforcements 56 of the first ply54, in comparision to the relatively lower modulus of elasticity of thenon-metal reinforcing fibers or cords of the second ply 58, means thatthe neutral bending axis A—A will perforce be closer to the more rigidfirst ply 54 of the sidewall segment 50. And so it follows that thecompressive forces placed upon the metal reinforcements 56 of the firstply 54 are large compared to the corresponding tensile stresses born bythe second ply 58.

During runflat operation, when the total compressive load F reaches amaximum value in the region of the sidewall 50 that is most immediatelyadjacent to the ground-contacting portion of the tire's tread (notshown), the radial compressive forces to which the more or less radiallyaligned metal reinforcing wires or cords 56 of the first ply 54 aresubjected necessarily impose upon the metal reinforcing wires or cordsthe potential for buckling. Such buckling corresponds to the kinds ofso-called column failures that, in the contexts of mechanical design,must be properly guarded against. Column failure is associated withlong, thin structural members loaded in axial compression. In the caseof the radially aligned, metallic reinforcing wires or cords 56 shown inFIGS. 2A and 2B, the effect of column failure, or buckling, of thereinforcing wires or cords of the first ply 54 can lead to severalresults including: (1) the runflat benefits of the supporting metallicwires or cords 56 will be defeated if the metallic reinforcementsbuckle; and (2) the radially aligned metallic elements, due to theextreme distortion associated with buckling, can become separated fromthe adjacent elastomeric components of the first ply 54 and also fromthe material of the wedge insert 52. Such separation of tire componentsrepresents a possible mode of tire failure and disintegration duringrunflat operation. Other modes of failure include heat buildup in thewedge insert 52 and fatigue failures of other tire components due tocyclical flexural effects as the uninflated but loaded tire rolls along.Another possible failure from the buckling is the breaking of the cordsdue to fatigue failure.

Principle of the Present Invention

The above-described potential for buckling of the radially aligned metalwires or cords 56 of the first or inner ply 54 shown in FIGS. 2A and 2Bcan be minimized or inhibited by the incorporation of additionalsupporting structures adjacent to the sidewall portions of the first ply54.

Before describing such additional supporting structures, the potentialfor buckling or column failure should be considered with regard to theplane within which such failure might take place. First, the respectivereinforcing metal wires or cords 56 are radially oriented and are moreor less parallel to one another as well as being closely mutuallyadjacent (as viewed from a side location that would be perpendicular tothe sidewalls). Thus, buckling failure of the respective wires or cords56 is most likely to occur in the direction that corresponds to thetire's circumferential direction, which is also common with the curvedplane of the first ply 54. However, the potential for buckling in anaxially outward direction, that is toward the wedge insert 52 isnecessarily prohibited or inhibited by the presence of the wedge.Therefore, effectively the only direction within which there exists thepossibility for a buckling failure is in the circumferential directionwhen the cords buckle in the plane of the sidewalls 22,24 in FIG. 1.While the inner liner 60 presents negligible support against axiallyinward-directed buckling of the metal wires or cords 56, especially whenthe tire is uninflated and the inner liner 60 is not even supported byair pressure, the curvature of the cords in the sidewalls prevents thebuckling in the axially inward direction. Thus the most likely directionof the buckling failure of the reinforcing wires or cords is in thecircumferential direction, primarily in the sidewalls of the tire.

Those skilled in the art might easily imagine that once the buckling ofthe metal wires or cords begins, the cyclical flexure associated withthe rolling of the uninflated or underinflated tire will lead eventuallyto fatigue failure of the metal monofilament wires or cords. Suchfatigue failures of the wires or cords 56 will further reduce theability of the sidewalls to support the uninflated tire's load. Inaddition, the broken ends of the failed wires or cords 56 have thepotential to pierce the inner liner 60 and perhaps even to penetrateinto the wedge insert sidewall reinforcement 52.

The present invention relates to the use of circumferentially disposedfabric treatments, as a way to provide anti-buckling support for themetal reinforcing wires or cords 56 of the first ply 54. Two types offabric treatment are described hereinafter.

FIG. 3 shows a fragmentary cross-sectional view of a sidewall segment 62that is similar in overall design to the sidewall segment 50 shown inFIGS. 2A and 2B. The sidewall segment 62 of FIG. 3 includes a wedgeinsert 64 disposed between a first or inner carcass ply 66 and a secondor outer carcass ply 68. The first carcass ply 66 is reinforced withmetal wires (monofilaments) or cords 70. (The first carcass ply 66 shownin FIG. 3 is essentially the same as the corresponding ply 54 shown inFIGS. 2A and 2B.) An inner liner 72 (which is essentially the same asthe inner liner 60 shown in FIGS. 2A and 2B) is disposed axially inwardof the second ply 68 (which is essentially the same as the secondcarcass ply 58 shown in FIGS. 2A and 2B.) The inventive feature of thepresent invention comprises the incorporation of two fabric layers74,76. The first fabric layer 74 is disposed between the inner liner 72and the first ply 66 while the second fabric layer 76 is disposedbetween the first ply and the wedge insert 64.

(NOTE: In FIGS. 2A, 2B, 3 and 4, such conventional tire components asthe inner liner, the ply layers and the wedge insert are essentially thesame despite the use of different identifying numbers in the respectiveFIGURES. For example, the wedge insert 52 in FIGS. 2A and 2B isessentially the same as the wedge inserts 64,82,128 a,128 b,168 a and168 b shown respectively in the subsequent FIGS. 3 through 6.)

Each of the fabric treatment layers 74,76 shown in FIG. 3 comprisesparallel-aligned cords which are oriented at angles of between 20 and 50degrees and preferably between angles of 30 degrees and 45 degrees withrespect to the circumferential direction. Typically, the fabric layer ismade of materials from the group of materials that include nylon,polyester, aramid and rayon. The cords constructed to have diameters ofbetween 0.2 millimeters (mm) and 1.5 mm, preferably between 0.3 mm and1.0 mm. The cord density is 15 to 50 ends per inch (epi) and preferably20 to 35 ends per inch. If the angle of the cords in the treatmentlayers 74,76 is less than 20°, the fabric prevents the tire from beingblown up subsequent to construction of the tire on the building drum.Alternatively, if the angle is more than 50°, the fabric has anegligible effect on preventing buckling in the circumferentialdirection during runflat operation as described hereinafter. The anglesof the respective cords within each fabric treatment 74,76 are oppositeto one another about the radial direction, which is to say they arecrossed with respect to one another. Thus, it follows that the fabriclayers 74,76 effectively attach or “tie” to one another each of theradially oriented metallic wires or cords 70 within the first ply 66.The benefit thereby derived is such that no single reinforcing cord 70can easily commence a circumferentially directed buckling withoutpulling along with it the most immediately adjacent reinforcing cords ofthe first ply 66. Buckling of the metal reinforcing wires or cords 70 isthereby inhibited during runflat operation wherein the wires or cordsare subjected to maximal compressive loading.

The radial height H denoted in FIG. 3 represents the portion of thesidewall's overall height within which the fabric layers 74,76 aredisposed. The height H corresponds to between 20 percent and 80 percentof the maximum radial reach, i.e. the length when the wedge insert isstraightened out, and preferably between 40 percent and 60 percent ofthe radial reach of the wedge insert. If the height of the fabric layers74,76 is less than 20 percent of the radial reach of the wedge insert,the fabric layers provide a negligible effect in preventing bucklingduring runflat operation. Alternatively, if the height H of the fabriclayers is more than 80% of the radial reach of the wedge insert, itsradially inwardmost and outwardmost portions will lie outside of thecompression area and will therefore add weight to the tire withoutadding any corresponding advantage. The fabric layers 74,76 are centeredmore or less across the radially central area of the circumferentiallydisposed wedge insert 64, which is also the region of maximumbending-stress-induced compressive loading of the metal-reinforced firstply 66 during runflat operation.

Those skilled in the art will recognize that a single woven fabriclayer, placed in direct contact with the first ply 66, will provide thesame anti-buckling benefit. FIG. 4 shows a fragmentary cross-sectionalview of a sidewall segment so that is similar in overall design to thesidewall segment 50 shown in FIGS. 2A and 2B and the sidewall segment 62shown in FIG. 3. The sidewall segment 80 of FIG. 4 comprises a wedgeinsert 82 disposed between a first carcass ply 84 and a second carcassply 86. The first carcass ply 84 is reinforced with metal wires or cords88. An inner liner 90 is disposed axially inward of the second ply 86.In this alternative embodiment of the present invention, the inventivefeature comprises a single woven fabric layer 92, which is disposedbetween the inner liner 90 and the first ply 84. Notice that the wovenfabric layer 92, located axially inward of the first ply 84, is mostadvantageously located with regard to inhibiting the above-describedcircumferential buckling potential of the metallic cords 88 of the firstor inner ply 84.

The radial height H denoted in FIG. 4 represents the portion of thesidewall's overall height within which the single woven fabric layer 92is disposed. The height H corresponds to between 20 percent and 80percent and preferably between 40 percent and 60 percent of the maximumradial reach of the wedge insert 82. The woven fabric layer 92 iscentered more or less across the radially central part of thecircumferentially disposed wedge insert 82, which is also the region ofmaximum bending-stress-induced compressive loading of themetal-reinforced first or inner ply 84 during runflat operation. Thewoven fabric layer 92 is made of woven threads made of a material fromthe class of materials that includes nylon, polyester, aramid and rayon.The threads have diameters of between 0.2 mm and 1.5 mm, preferablybetween 0.3 mm and 1.0 mm. The fabric is woven to a density of between15 epi and 50 epi, preferably between 20 epi and 35 epi. The woventhreads of the material cross each other and are at an angle of between20 and 50 degrees and preferably at an angle of between 30 and 45degrees so that the threads cross the cords of ply 84 against which thewoven material is applied.

The Invention in Relation to the Prior Art U.S. Pat. No. 3,386,486('486) by Kovac describes a tire construction in which radial and biasplies are sandwiched between one another. The fabric bias plies do notreach radially inward to the beads, as do the radial plies. The '486patent can be distinguished from the present invention in that theformer: (1) does not describe a runflat tire; (2) discloses fabric biasplies that are not restricted to the sidewall regions; (3) the first orinner ply is not metal reinforced; and (4) the bias plies are do notserve the purpose of inhibiting compression-induced buckling of theradial plies.

U.S. Pat. No. 2,430,560 ('560) by Elliot describes a tire constructionin which a plurality of ply layers sandwich with one another for theexpressed purpose (paraphrasing) of providing zones of increasedstretchability in the sidewall portions of the casing adjacent to thebead portions (see column 1, lines 28+ of the '560 patent). Thesidewalls of '560 are accordingly isolated from the bead regions interms of relative flexibility such that while the sidewalls are givengreater rigidity, flexing is possible in the radially inwardmost regionsthat are near to the beads. Thus while '560 patent provides rigidsidewalls, the tire is not per se a runflat tire nor does it use any ofthe multiple and mutually sandwiching plies to inhibit buckling ofcompression loaded reinforcing cords, metal or otherwise, of othercarcass ply layers. Moreover, none of the sandwiching layers isrestricted exclusively to the sidewall regions.

U.S. Pat. No. 1,393,952 ('952) by Miller has FIGURES showing a pluralityof plies similar to those shown in the FIGURES of the '560 patentdescribed hereinbefore. “Outside and inside plies of fabric and cordalternate plies of fabric and cord alternate all the way through theside wall immediately above the bead . . . ” (col. 1, 11. 19+). Thus,while the '952 patent provides rigid sidewalls due to the many layers ofplies, the tire is not, as with the '560 patent described before, per sea runflat tire nor does it use any of the multiple and mutuallysandwiching plies to inhibit buckling of compression loaded reinforcingcords, metal or otherwise, of other carcass ply layers. Also, as with'560 patent above, none of the sandwiching layers is restrictedexclusively to the sidewall regions, but rather to the bead regionswhere the operation intend is other than inhibition ofcompression-induced buckling of ply reinforcing cords, metal orotherwise.

European Patent Document 0 507 184 A1 ('184) by Johnson describesbias-ply reinforcing fabric layers in the outer portions of sidewalls ofan EMT tire or runflat tire. The main intent of the invention describedin the '184 document is to provide an EMT tire having a high sectionheight, i.e., a high-profile tire. A bias-ply layer extends across thesidewall regions from beneath the axially outwardmost portions of thesteel belts and thence radially inward to a location that is bothradially inward of the turnup ends and radially inward of the radiallyoutwardmost portion of the apex in each bead region. The bias-ply layersof the '184 document are, however, located immediately axially outwardof the second or outermost full carcass ply layer that extends from beadto bead. Each of the two bias-ply layers “provides an increasedstiffness in the side wall due to the sheer loading therebetween whenthe tire is in the run flat condition” (col. 7, 11. 23+). Thus '184differs from the present invention in the specific following ways: (1)the bias-ply fabric layer, which is equivalent to the single wovenfabric treatment of the present invention, is intended to bear tensionduring runflat operation; and (2) it is not intended to inhibit bucklingof metal-reinforcing cord members of any other part of the tire.

European Patent Document 0 475 258 A1 ('258) by Ghilardi describes anEMT tire having a fabric layer 17 (called “textile reinforcing strip” incol 6, 1. 44 and referred to as “strips” in col. 8, 1. 39). While thefabric layer 17 is disposed axially inward of and adjacent to the firstor inner ply, its function seems to be intended to carry compressionloading rather than, as with the present invention, to inhibit bucklingof the reinforcing cords of the first carcass ply during runflatoperation.

Embodiments

A first embodiment of the invention is illustrated in FIG. 5, whichshows a cross-sectional view of a pneumatic radial ply EMT or runflattire 100. The tire 100 has a tread 102, a belt structure 104 comprisingbelts 106,108, a fabric overlay 110 disposed between the tread and thebelt structure, a pair of sidewall portions 112,114, and a carcassstructure 118. The carcass 118 comprises a first or inner ply 120 and asecond or outer ply 122, a pair of bead regions 116 a,116 b, and agas-impervious inner liner 124. The bead regions 116 a,116 b comprise apair of beads 124 a,124 b, respectively, and a pair of bead fillerapexes 126 a,126 b, respectively. The sidewalls 112,114 each contain onesidewall wedge insert 128 a,128 b, each of which is disposed between thefirst ply 120 and the second ply 122. The first ply 120 is metalreinforced and, in the two sidewall regions, is sandwiched between andsupported by and buttressed against compressive-load-induced bucklingduring runflat operation by circumferentially disposed first fabrictreatment layers 130 a,130 b (compare treatment layers 74), locatedbetween the first carcass ply 120 and the inner liner 124, andcircumferentially disposed second fabric treatment layers 132 a,132 b(compare treatment layers 76) located between the first carcass plylayer 120 and the wedge insert 128 a,128 b, respectively.

A second embodiment of the invention is illustrated in FIG. 6, whichshows a cross-sectional view of a pneumatic radial ply EMT or runflattire 140. The tire 140 has a tread 142, a belt structure 144 comprisingbelts 146,148, a fabric overlay 150 disposed between the tread and thebelt structure, a pair of sidewall portions 152,154, and a carcassstructure 158. The carcass 158 comprises a first or inner ply 160, asecond or outer ply 162, a pair of bead regions 156 a,156 b, and agas-impervious inner liner 164. The bead regions 156 a,156 b eachcomprise beads 159 a,159 b, respectively, and bead filler apexes 166a,166 b, respectively. The sidewalls 152,154 each contain at least onesidewall wedge insert 168 a,168 b, respectively, disposed between thefirst or inner carcass ply 160 and the second or outer carcass ply 162.A second insert 169 a,169 b between the inner liner 164 and the innerfirst carcass ply 160 can also be provided, as desired, for eachembodiment. The first carcass ply 160 is metal reinforced and, in thesidewall regions 152,154, is supported by and buttressed againstcompressive-load-induced buckling during runflat operation bycircumferentially disposed woven fabric treatment layers 170 a,170 b,respectively, (compare fabric treatment 92) located between the firstcarcass ply and the inner liner 164.

While the invention has been described in combination with embodimentsthereof, it is evident that many alternatives, modifications, andvariations will be apparent to those skilled in the art in light of theforegoing teachings. Accordingly, the invention is intended to embraceall such alternatives, modifications and variations as fall within thespirit and scope of the appended claims.

What is claimed is:
 1. A pneumatic radial ply runflat tire having acarcass comprising: an inner liner, an inner carcass ply reinforced withsubstantially radially aligned metal wires and disposed axially outwardof the inner liner, an outer carcass ply disposed axially outward of theinner carcass ply, and a wedge insert disposed circumferentially in asidewall region of the tire between the inner carcass ply and the outercarcass ply, and a first fabric layer comprising cords and disposedcircumferentially in the sidewall region of the tire between the innerliner and the inner carcass ply, and a second fabric layer comprisingcords and disposed circumferentially in the sidewall region of the tirebetween the inner carcass ply and the wedge insert, wherein the innercarcass ply is sandwiched between the first and second fabric layers. 2.Tire, according to claim 1, wherein: the cords of the first fabric layerare parallel-aligned.
 3. Tire, according to claim 1, wherein: the cordsof the first fabric layer have both radially inwardmost and radiallyoutwardmost portions disposed within the sidewall region.
 4. Tire,according to claim 1, wherein: the cords of the first fabric layer areoriented at angles of between 20 and 50 degrees with respect to acircumferential direction of the tire.
 5. Tire, according to claim 1,wherein: the cords of the first fabric layer are oriented at angles ofbetween 30 and 45 degrees with respect to a circumferential direction ofthe tire.
 6. Tire, according to claim 1, wherein: the cords of the firstfabric layer have diameters of between 0.2 millimeters (mm) and 1.5 mm.7. Tire, according to claim 1, wherein: the cords of the first fabriclayer have diameters of between 0.3 millimeters (mm) and 1.0 mm. 8.Tire, according to claim 1, wherein: the cords of the first fabric layerhave a cord density of 15 to 50 ends per inch (epi).
 9. Tire, accordingto claim 1, wherein: the cords of the first fabric layer have a corddensity of 20 to 35 ends per inch (epi).
 10. Tire, according to claim 1,wherein: the first fabric layer comprises a material selected from thegroup consisting of nylon, polyester, aramid and rayon.
 11. Tire,according to claim 1, wherein: the wedge insert has a radial reachwithin the sidewall of the tire, and the first fabric layer has a radialwidth of between 20 percent and 80 percent of the reach of the wedgeinsert.
 12. Tire, according to claim 1, wherein: the wedge insert has aradial reach within the sidewall of the tire, and the first fabric layerhas a radial width of between 40 percent and 60 percent of the reach ofthe sidewall insert.
 13. Tire, according to claim 1, wherein: the firstfabric layer is centered substantially across a radially central area ofthe wedge insert.
 14. Tire, according to claim 1, wherein: the firstfabric layer is in direct contact with the inner carcass ply.
 15. Tire,according to claim 1, wherein: the cords of the first fabric layer areparallel-aligned, the cords of the second fabric layer areparallel-aligned, and the respective parallel-aligned cords of the firstand second fabric layers are oriented at opposite angles of between 20degrees and 50 degrees with respect to a circumferential direction ofthe tire.
 16. Tire, according to claim 1, wherein: the cords of thefirst fabric layer are oriented at angles between 20 and 50 degrees withrespect to a circumferential direction of the tire, and the cords of thesecond fabric layer are oriented at angles between 20 and 50 degreeswith respect to a circumferential direction of the tire.
 17. Tire,according to claim 16, wherein: the cords of the first fabric layer havediameters of between 0.2 millimeters (mm) and 1.5 mm, and the cords ofthe second fabric layer have diameters of between 0.2 millimeters (mm)and 1.5 mm.
 18. Tire, according to claim 1, wherein: the cords of thefirst fabric layer have a cord density of 15 to 50 ends per inch (epi),and the cords of the second fabric layer have a cord density of 15 to 50ends per inch (epi).
 19. Tire, according to claim 1, wherein: the wedgeinsert has a radial reach within the sidewall of the tire, and the firstfabric layer has a radial width of between 20 percent and 80 percent ofthe reach of the wedge insert, and the second fabric layer has a radialwidth of between 20 percent and 80 percent of the reach of the wedgeinsert.
 20. Tire, according to claim 1, wherein: the cords of the secondfabric layer are oriented at angles of between 30 and 45 degrees withrespect to a circumferential direction of the tire.